After installing, go to your project → "Devices & Networks" → right-click your CPU → "Change device" → select the new "FW 4.3" version under the HSP category. Then download again.
HSP0276 (Hardware Support Package) for SIMATIC S7-1200, Firmware V4.3 Target Environment: TIA Portal (versions V17, V18, V19) Review: A Critical Bridge for Modern S7-1200 Development Overall Rating: 4.5/5 hsp0276 s71200 cpu v4.3
4.5/5 (Deducted 0.5 for the manual installation friction). After installing, go to your project → "Devices